1. Field of the Invention
The present invention is related to a circuit for recognizing a beginning and a data rate of data and method thereof, and particularly to a circuit for recognizing a beginning and a data rate of data and method thereof according to an alignment pattern corresponding to a data rate.
2. Description of the Prior Art
Each data rate of data has a corresponding alignment pattern. When the data is transmitted from a device to a host, the host recognizes the data rate of the data and a beginning of the data according to the corresponding alignment pattern. In addition, the host uses the data rate to communicate with the device after the data rate of the data is recognized.
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a circuit 100 for recognizing a beginning and a data rate of data according to the prior art. The circuit 100 includes a data rate detecting unit 102 and a post processing unit 104. The data rate detecting unit 102 detects a data rate (such as a data rate V1) one time, where at least one data rate is available between a host 106 and a device 108. When the data rate detecting unit 102 does not detect an alignment pattern corresponding to the data rate V1 in data transmitted between the host 106 and the device 108 after a predetermined time, the data rate detecting unit 102 starts to detect a data rate V2, and so on. However, the data rate detecting unit 102 only detects one data rate at a time, so if the data rate detecting unit 102 spends too much time detecting the data rate of the data, a clock and data recovery of a system may fail. In addition, if the host 106 can support a higher data rate, the data should be transmitted at the higher data rate between the host 106 and the device 108. But, in the prior art, during establishing a synchronous data rate (handshaking) between the host 106 and the device 108, the host 106 may use a lower data rate to communicate with the device 108 instead of using a higher data rate to communicate with the device 108.